Changes in the physicochemical properties of maize endosperm, endosperm fractions, and isolated starches because of nixtamalization

This work focused on the physicochemical changes undergone by maize endosperm during a thermo-alkaline nixtamalization process for the cooking (0 h) and steeping (8 h) steps. The study was performed on the outermost 10%, subsequent 10%, and the remaining 80% of crude, cooked (0 h), and steeped (8 h) endosperm. Calcium content increased mainly in the outermost layers of the endosperm, while the remaining 80% showed no significant changes. The starch granules showed no external damage during cooking and steeping. X-ray analysis revealed that the hard endosperm contained A-type starch with an orthorhombic crystalline structure. Examination of the isolated starches during nixtamalization showed that there is a fraction that does not undergo physicochemical transformation when in contact with water and heat, and this fraction can be referred to as resistance starch. A new methodology using scanning electron microscopy has shown that the pasting properties are determined by the changes in the morphology of the paste.